Season 4 (2011)

All 13 episodes from the fourth series of the BBC fantasy drama set in the mythical city of Camelot. The show follows the relationship between the young King Arthur (Bradley James) and Merlin (Colin Morgan), the wise sorcerer who guides him to power and beyond. In this series, the increasing power of Morgana (Katie McGrath), Merlin's protégé turned rival, poses an ever-growing threat to Arthur's fledgling kingship. The episodes are: 'The Darkest Hour', 'The Darkest Hour: Part 2', 'The Wicked Day', 'Aithusa', 'His Father's Son', 'A Servant of Two Masters', 'The Secret Sharer', 'Lamia', 'Lancelot du Lac', 'A Herald of the New Age', 'The Hunter's Heart', 'The Sword in the Stone: Part One' and 'The Sword in the Stone: Part Two'.

Season 5 (2012)

Merlin finds himself locked in a battle unlike any he has fought before; Arthur summons his father from the dead; and Morgana uses Princess Mithian (Janet Montgomery) as bait to lure Arthur to his death.